Add GetPropertyPriority to CSSStyleDeclaration

Tweak getPropertyPriority to match recommendations

Adding Tests for Style Priority

Use else if

Adding Content Test for GetPropertyPriority

Revert "Adding Tests for Style Priority"

This reverts commit 8666a37f833b06c3e43f27acd8a9678e94425e55.

components/script/dom/cssstyledeclaration.rs

@@ -69,6 +69,7 @@ impl CSSStyleDeclaration {
 
 trait PrivateCSSStyleDeclarationHelpers {
     fn get_declaration(self, property: &Atom) -> Option<PropertyDeclaration>;
+    fn get_important_declaration(self, property: &Atom) -> Option<PropertyDeclaration>;
 }
 
 impl<'a> PrivateCSSStyleDeclarationHelpers for JSRef<'a, CSSStyleDeclaration> {
@@ -77,6 +78,12 @@ impl<'a> PrivateCSSStyleDeclarationHelpers for JSRef<'a, CSSStyleDeclaration> {
         let element: JSRef<Element> = ElementCast::from_ref(*owner);
         element.get_inline_style_declaration(property).map(|decl| decl.clone())
     }
+
+    fn get_important_declaration(self, property: &Atom) -> Option<PropertyDeclaration> {
+        let owner = self.owner.root();
+        let element: JSRef<Element> = ElementCast::from_ref(*owner);
+        element.get_important_inline_style_declaration(property).map(|decl| decl.clone())
+    }
 }
 
 impl<'a> CSSStyleDeclarationMethods for JSRef<'a, CSSStyleDeclaration> {
@@ -144,6 +151,30 @@ impl<'a> CSSStyleDeclarationMethods for JSRef<'a, CSSStyleDeclaration> {
         }
     }
 
+    // http://dev.w3.org/csswg/cssom/#dom-cssstyledeclaration-getpropertypriority
+    fn GetPropertyPriority(self, property: DOMString) -> DOMString {
+        // Step 1
+        let property = Atom::from_slice(property.as_slice().to_ascii_lower().as_slice());
+
+        // Step 2
+        let longhand_properties = longhands_from_shorthand(property.as_slice());
+        if let Some(longhand_properties) = longhand_properties {
+            // Step 2.1 & 2.2 & 2.3
+            if longhand_properties.iter()
+                                  .map(|longhand| self.GetPropertyPriority(longhand.clone()))
+                                  .all(|priority| priority.as_slice() == "important") {
+
+                return "important".to_string();
+            }
+        // Step 3
+        } else if self.get_important_declaration(&property).is_some() {
+            return "important".to_string();
+        }
+
+        // Step 4
+        "".to_string()
+    }
+
     // http://dev.w3.org/csswg/cssom/#dom-cssstyledeclaration-setproperty
     fn SetProperty(self, property: DOMString, value: DOMString,
                    priority: DOMString) -> ErrorResult {

components/script/dom/element.rs

@@ -469,6 +469,7 @@ pub trait ElementHelpers<'a> {
     fn remove_inline_style_property(self, property: DOMString);
     fn update_inline_style(self, property_decl: style::PropertyDeclaration, important: bool);
     fn get_inline_style_declaration(self, property: &Atom) -> Option<style::PropertyDeclaration>;
+    fn get_important_inline_style_declaration(self, property: &Atom) -> Option<style::PropertyDeclaration>;
 }
 
 impl<'a> ElementHelpers<'a> for JSRef<'a, Element> {
@@ -595,6 +596,16 @@ impl<'a> ElementHelpers<'a> for JSRef<'a, Element> {
                         .map(|decl| decl.clone())
         })
     }
+
+    fn get_important_inline_style_declaration(self, property: &Atom) -> Option<style::PropertyDeclaration> {
+        let inline_declarations = self.style_attribute.borrow();
+        inline_declarations.as_ref().and_then(|declarations| {
+            declarations.important
+                        .iter()
+                        .find(|decl| decl.matches(property.as_slice()))
+                        .map(|decl| decl.clone())
+        })
+    }
 }
 
 pub trait AttributeHandlers {

components/script/dom/webidls/CSSStyleDeclaration.webidl

@@ -14,7 +14,7 @@ interface CSSStyleDeclaration {
   readonly attribute unsigned long length;
   getter DOMString item(unsigned long index);
   DOMString getPropertyValue(DOMString property);
-  //DOMString getPropertyPriority(DOMString property);
+  DOMString getPropertyPriority(DOMString property);
   [Throws]
   void setProperty(DOMString property, [TreatNullAs=EmptyString] DOMString value,
                                        [TreatNullAs=EmptyString] optional DOMString priority = "");